CNSC User Support

The BULLx cluster uses so called front-end nodes or login nodes for interactive access and the submission of batch jobs.

LIGER has two different login nodes (login01 and login02) which may be addressed in 2 ways:

• from somewhere on the ECN network authenticated on the cluster network;
• from somewhere without an authenticated ECN account, you need to request first a new user account with a valid ip address declared.

liger.ec-nantes.fr

The front-end nodes have an identical environment, but multiple sessions of one user may reside on different nodes which must be taken into account when killing processes.

A login node is in terms of hardware equivalent to a cluster node, but has more memory, is connected to the external network, and does not run jobs itself. It is intended for:

• compiling code
• developing applications
• submitting applications to the cluster for execution
• monitoring running applications
• post-processing and managing data.

Only the login nodes can be accessed interactively from the outside world via Secure Shell.

Users can't login by suppling username/password credentials. Instead, password free login based on SSH key exchange is required.

The public/private ssh key pair has to be generated on the system from which you want to access LIGER and stored in the directory. On Linux or UNIX-based systems, the key pair can be generated by executing

# ssh-keygen -t [dsa|rsa]

Please protect the ssh key with a non-trivial pass phrase to fulfill the ECN security policy. (For further details on ssh key generation see FAQ: How to generate ssh keys)

The generated public ssh key contained in the file id_dsa.pub or id_rsa.pub on your system must be uploaded through the JSC WEB interface when initially applying for a userid and will be appended to /.ssh/authorized_keys.

In case your ssh key got lost or needs to be updated, you can use the dispatch ssh-key upload page, to upload a new key. In either case the key will be put to the file

/.ssh/authorized_keys

on the LIGER system.

Note: Please make sure that your directory is not open for write access for other groups or world, otherwise .ssh will not work.

On Windows OS it does not have SSH capabilities built-in. You must download PuTTY or Bitvise Tunnelier. Enter hostname: liger.ec-nantes.fr. Click connect and enter your username and password when prompted. Once connected you can run commands. After that a typical login looks like

# ssh <userid>@liger.ec-nantes.fr

liger is a generic name which will either establich a connection to login01 or login02.

Comment: Too many accesses (ssh or scp) within a short amount of time will be interpreted as intrusion and leads to automatic disabling the origin system at the ICI firewall. For transferring multiple files in a single scp session the -r option can be used, which allows to transfer a whole directory.

If a login is done via multiple machines, the X11 forwarding must be enabled in the file .ssh/config with:

PubkeyAuthentication yes
ForwardAgent yes
ForwardX11 yes

The Secure Shell rsa public keys for the interactive nodes are given in the following link (please add these to ~/.ssh/known_hosts on your own workstation before logging in for the first time): SSH Public Key

LIGER users have access to their home data in a common General Parallel File System (GPFS). For organization of the home data in respect to using multiple systems it is strongly recommended to add new subdirectories in for new machines.

Attention! Please do NOT rename or reorganize the directory structure of the existing directories because this will cause recall and backup activities for every changed file due to path or name modifications.

The Login Shell on each system points to system's favored shell: bash

Users are not allowed to change the Login Shell but they can switch to a personal shell within the login process. User's will find a template within the initial .profile in .

The Linux system of the front-end nodes has 64 GB of main memory.
Default user limit: To prevent overloading the memory, the sessions have a hardlimit of 3 GB each.

Limits can be checked with the command:
Check for: virtual memory (kbytes, -v)
The limit specification is in KBytes.

• for memory

  ulimit -v

• for all limits

  ulimit -a

The persistent settings of the shell environment are governed by the content of .bashrc , .profile or scripts sourced from within these files. Please use these files for storing your personal settings.

If you're new to using a shell, look over this list of common commands. If you're really curious about what can be done here is a comprehensive list of SSH commands.